Last week Hillary Rodham Clinton delivered an important economic address, Gov. Scott Walker of Wisconsin formally announced his candidacy for the White House, Sen. Bernie Sanders of Vermont explained how he hopes to win the allegiance of blue-collar voters, and Gov. Chris Christie made nice to Donald Trump even as he criticized his remarks on immigration.

But by far the most important sentence uttered in the political world last week came from someone not running for president — but whose views and actions will shape the next presidency. Here’s that vital sentence:

There’s no limit to the number of taxes that Bernie Sanders and Hillary Clinton want to raise, and there’s no limit to the amount of new government they want to create.

Of course, most of this, from House Speaker John Boehner of Ohio, is harmless pre-election rhetoric, unremarkable bogey-talk from the right about high taxes and big government. (There’s an analogous bogey vocab on the left, excoriating the heartlessness and economic royalism — a term from Franklin Roosevelt’s 1936 acceptance speech — of conservatives. It’s equally vapid.) Now zero in on Mr. Boehner’s sentence and its real power comes from just five words: Bernie Sanders and Hillary Clinton.

But if you really want to distill it to its incendiary essence you might concentrate on a single word: and.

That simple conjunction links Mr. Sanders and former Secretary of State Clinton, and neither can be happy about that. But it is a formidable word, and you can bet it will not be the last time you hear it. Its meaning is that Mr. Sanders and Ms. Clinton are what former Gov. George Wallace, in a stinging 1968 reference to former Vice President Richard M. Nixon and Vice President Hubert H. Humphrey, described as “Tweedle-dum and Tweedle-dee,” explaining, “There’s not a dime’s worth of difference between the two.”

A dime in 1968 is the equivalent of 69 cents now — remember that when you complain about the cost of a Hershey bar — so Mr. Boehner, channeling Mr. Wallace, is basically saying there isn’t 69 cents worth of difference between Ms. Clinton and Mr. Sanders.

Put aside the notion that there probably isn’t 69 cents worth of difference among most of the 16 declared Republican candidates, apart from Mr. Trump, whom we might consider the New Horizons candidate, given that his views come from the distant extremities of the solar system, somewhere far away, near Pluto. In any case the Republicans’ problem is that their field is a fuzzy mush lacking distinctiveness, though — accounting for the political records of a number of the contenders — possessing some distinction.

But as the Republicans spent the past several weeks putting distance between themselves and Mr. Trump, Ms. Clinton tried to distinguish herself from Mr. Sanders — even as she tried to co-opt his issues. The Republican task was much the easier job (Rx: Simply say that Mr. Trump is out there, like Pluto). Ms. Clinton’s requires the agility of a figure skater (Rx: the political equivalent of a toe loop, a flip and a triple Lutz).

The first principle of the Clinton campaign is to be a supermarket — Stop & Shop, or Giant Eagle, or Safeway, or Kroger, which is to say having something for everyone, above all to be familiar, unthreatening, even a bit bland. The moment she comes across as Whole Foods — a little exotic, a little elitist — she’s cooked, wild king salmon left on the grill too long.

But the second principle of the Clinton campaign is to make sure she dangles a few items from the cheese boutique and the wine-and-spirits emporium down the street.

On the surface this seems contradictory, like a nice Riesling with a fatty pork chop and a pile of frozen crinkle fries. But that’s the Clinton task; above all she has to possess conventional economic views for the general election along with — and here the gustatory imagery breaks down — some red meat for the pink-tinted liberals.

That’s why her speech in New York contained strains of Bernie (the economy is “stacked for those at the top”) along with strains of Bill (“Under President Clinton — I like the sound of that — America saw the longest peacetime expansion in history”).

It had some bows to Barack (“President Obama saved the auto industry, imposed new rules on Wall Street and provided health care to 16 million Americans”) but also some nostrums of Newt (“Small businesses create more than 60 percent of new American jobs on net. So they have to be a top priority” — right out of the playbook of former House Speaker Gingrich, who sought to move the GOP from being the party of big business to being the voice of small business).

Overall it was a deft performance, balancing fiery populism about Wall Street excesses without coming out for busting up the banks. But Ms. Clinton is going to have to be the political equivalent of a Wallenda, for she is performing a high-wire act.

The Republicans have a balancing act to perfect themselves, and it came into focus last week with the release of a new book by Arthur C. Brooks, president of the American Enterprise Institute. It’s called “The Conservative Heart,” and the subtitle sets out the challenge: “How to Build a Fairer, Happier and More Prosperous America.” Note the presence of the word “and.”

Conservatives of the old school — think Calvin Coolidge, Robert Taft, Karl Mundt, Richard Nixon — weren’t known for harping on happiness. They battled Communists and big spenders and didn’t care all that much if the country was in a serene reverie, especially in the Cold War years when containment trumped contentment.

But Mr. Brooks argues that happiness is the “central expression of the conservative heart” and he sets forth a “happiness portfolio,” which predictably includes a celebration of the free-enterprise system but surprisingly includes this uplifting notion: “Resist the worldly formula of misery, which is to use people and love things.”

So there is a whole lot of balancing going on in American politics today — a little of this plus a little of that, all in the search for perfect equipoise. It requires the promiscuous use of the word “and,” the very word that highlights the challenge the 2016 candidates face, starting with Ms. Clinton.

David Shribman, a Pulitzer Prize winner in journalism, is executive editor of the Pittsburgh Post-Gazette.